Electrical connectors that can be connected and disconnected underwater are well-known in single and multiple pin types. The usual structure comprises a socket or female portion with electrical connections enclosed in a sealed chamber. The chamber is often filled with a dielectric fluid or semi-mobile compound (grease or gel) to minimize arcing and water contamination. The electrical connection takes place when a male contact probe penetrates the chamber and engages the female contact elements therein. The greatest problem is to keep water from entering the interior of the chamber and to keep the dielectric filler from leaking out, particularly during mating and unmating. Several schemes have been employed in the past to accomplish this.
Fluid filled connectors can be adequately sealed using blade type male pins of flat cross-section in combination with a resilient sealing element having normally closed, penetrable slits. A good example is disclosed in my U.S. Pat. No. 3,643,207, entitled Sealed Electrical Connector. Other fluid filled connectors are sealed by having cylindrical probes that involve mating seals and shuttle pistons driven by springs. Examples are shown in U.S. Pat. Nos. 4,188,084; 4,039,242 and 4,174,875. Connectors of this second type having pistons, springs and sliding seals are complex and expensive.
Connectors having chambers filled with semi-mobile dielectric compounds have used small diameter male probes of round cross-section in combination with perforated resilient seals held normally closed by compression to solve the sealing problem. A single round pin type is illustrated in my U.S. Pat. No. 3,522,576 entitled Underwater Electrical Connector. Another example involving multiple round pins penetrating resilient seals into a chamber filled with a semi-mobile dielectric compound is described in U.S. Pat. No. 3,972,581.
For reasons which will now be discussed, male contact probes having round cross-section that can be of variable diameter along their length, are superior to blade type probes of flat cross-section in many applications. Round probes are stronger than flat probes of equal cross-section. Round probes create radially symmetrical electric fields, and so do not have sharp field maxima with the associated problems of insulation difficulties and electrical leakage. Round probes are easier and cheaper to manufacture. Most importantly, round probes lend themselves to applications involving multiple electrical contacts arranged coaxially in a single male probe.
Connectors with fluid filled chambers are superior in many applications to connectors with chambers filled with semi-mobile dielectric compounds. Fluid, by virtue of its mobility, can respond rapidly to changes in ambient pressure. Because of this sensitivity, fluid filled connectors can be used in applications calling for connectors that are unaffected by explosions in the nearby environment. Fluid can also respond rapidly to volume displacement, as occurs with the rapid withdrawal of the male probe from the chamber. A semi-mobile compound will often cavitate in similar circumstances, thereby pulling in the more mobile air or water from the exterior to fill the void created by the withdrawn probe instead of actuating a volume compensating mechanism usually provided within the chamber itself. For the same reason of restricted mobility, the rapid insertion of a male probe into the chamber will sometimes result in the compound being extruded past the probe and out of the chamber instead of actuating the volume compensator. More important than this, however, is the fact that semi-mobile compound can support contaminants in paths or fissures within the compound. For example, a male probe repeatedly entering and leaving a chamber filled with semi-mobile compound will always travel the same path from exterior environment to female contact element through the same bit of compound, as the compound does not move readily within the chamber. Thus contaminants entering with the probe each time it penetrates continue to build up in the compound in a direct path between the female electrical contact and the outside environment, resulting in degradation of the electrical characteristics of connector. In contrast, contaminants entering a fluid filled connector, due to the mobility of the fluid, disperse in suspension throughout the fluid in the chamber and so do not concentrate in a direct path between the interior contacts and the outside environment. Furthermore, since the fluid chosen as a filler is usually an oil, any water entering the chamber forms a small bead within the oil rather than a fissure, and so does not tend to bridge the gap to the exterior environment or to other contacts within the chamber.
As may be understood for many applications, the most advantageous connector of this general type would be one utilizing male probes of round cross-section penetrating a perforated resilient seal into a chamber filled with dielectric fluid. None of the above mentioned patents solves the problem of providing a connector in which a simple male probe of round cross-section, and which may have multiple coaxial contacts, can be sealably inserted and withdrawn from a dielectric fluid filled chamber, repeatedly and without tools or accessory equipment.